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941.
David L. Willey Karsten Fischer Elmar Wachter Thomas A. Link Ulf-Ingo Flügge 《Planta》1991,183(3):451-461
Using an 5-AvaII fragment of the spinach (Spinacia oleracea L.) phosphate translocator cDNA as a probe for a hybridization screening of a pea (Pisum sativum L.) cDNA library we have cloned and sequenced a cDNA clone coding for the phosphate translocator precursor protein from pea chloroplasts. The full-length cDNA clone comprises 42 base pairs (bp) at the 5-non-coding region, a 1206-bp coding region corresponding to a polypeptide of 402 amino-acid residues (relative molecular mass 43 671) and 244 bp at the non-coding 3-region. Determination of the N-terminal sequence of the phosphate translocator from both pea and spinach chloroplasts revealed that the transit peptides consist of 72 and 80 amino-acid residues, respectively. These transit peptides are different from those of other chloroplastic transit peptides in that they both contain an amphiphilic -helix which is located either in close proximity to the processing site in pea or at the N-terminus in spinach. The mature proteins from pea and spinach both contain about 87% identical amino-acid residues and about seven putative membrane-spanning -helices. Some of these -helices have an amphiphilic character and might serve to form a hydrophilic translocation channel through the membrane. The in-vitro synthesized pea precursor protein is directed to the chloroplast and inserted into the chloroplast envelope membrane.Abbreviations bp
base pairs
- kDa
kilodaltons
- Mr
relative moleculas mass
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
We wish to thank Dr D. Pappin and R. Jakes (AFRC Sequencing Laboratory, Department of Biochemistry, University of Leeds, UK) for performing the N-terminal sequence determinations and are greatful to Dr J. S. Gantt (Botany Department, University of Georgia, Athens, USA) for a pea leaf cDNA library and to Professor J. C. Gray (University of Cambridge, Department of Botany, Cambridge, UK) for helpful discussions. This work was supported by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, the Science and Engineering Research Council and the Royal Society. D.L.W. was the recipient of the Royal Society Rosenheim research fellowship and K.F. was supported by a fellowship from the Studienstiftung des deutschen Volkes. 相似文献
942.
L. D. Bergelson 《Bioscience reports》1989,9(1):27-40
Using high density and low density lipoproteins (HDL and LDL) labeled with fluorescent analogues of phosphatidylcholine or sphingomyelin it was found that low amounts (10–12 M) of prostaglandins E1 and F2 induced different structural rearrangements of the lipoprotein surface, whereas prostaglandins E2 and F1 had no effect. The effects of prostaglandin E1 on HDL were largely paralled by those of this prostaglandin on synthetic recombinants prepared from pure apolipoprotein A1, phospholipids and cholesterol and were demonstrated to be caused by prostaglandin-apolipoprotein interaction. The interaction resembled that of a ligand with a specific receptor protein because it was specific, reversible, concentration and temperature dependent and saturable. However the retaining capacity of HDL or LDL for prostaglandin E1 as determined by equilibrium dialysis was very low and a single prostaglandin E1 molecule was able to induce structural changes in large numbers of discrete lipoprotein particles. To explain this remarkable fact a non-equilibrium model of ligand-receptor interaction is proposed. According to that model in open systems characterized by weak ligand-receptor binding, high diffusion rate of the ligand and long relaxation times which exceed the interval between two successive receptor occupations, the ligand-induced changes will accumulate, resulting in transformation of the system into a new state which may be far away from equilibrium. It is emphasized that the low mobility of lipids constituting the environment of the receptor protein plays a critcal role in this type of signal amplification.It was further demonstrated that the PGE1-induced changes of the lipoprotein surface resulted in an enhancement of LDL-to-HDL transfer of cholesterol esters and phosphatidylcholine especially in the presence of serum lipid transfer proteins. The acceleration of the interlipoprotein transfer caused by prostaglandin E1 in turn increases the rate of cholesterol esterification in serum. It is suggested that in such a way prostaglandin E1 may influence the homeostasis of cholesterol.Abbreviations LDL
low density lioproteins
- HDL
high density lipoproteins
- PG
prostaglandin
- ASM
anthrylvinyl-labeled sphingomyelin (N-12-(9-anthryl)-11-trans-dodecanoylsphingosin-1-phosphocholine
- APC
anthrylvinylphosphatidylcholine (1-radyl-2-[(9-anthryl)-11-transdodecanoyl)-sn-glycerophosphocholine
- NAP-SM
nitroazidophenyl labeled sphingomyelin (N-[N-(2-nitro-4azidophenyl)-12-aminododecanoyl]-sphingosin-1-phosphocholine)
- NAP-PC
adizophenyl labeled phosphatidylcholine (1-radyl-2-[N-(2-nitro-4azidophenyl)-12-aminododecanoyl]-sn-glycero-3-phosphocholine
- DPPC
dipalmitoylphosphatidylcholine
- P
fluorescence polarization
- E
parameter of tryptophanyl to ASM resonance energy transfer
- LEP
lipid-exchange protein 相似文献
943.
Summary A super strain ofBacillus firmus (NCIM-2636) producing a phytohormone, indole-3-acetic acid, in addition to its high ability to solubilize insoluble inorganic
phosphates were applied in acid soils of Nagaland, India. Rice (Oryza sativa L.) variety Jaya and IR-8 were grown in kharif season in two successive years 1980 and 1981. After proper manuring the soils
received single super phosphate (S.S.P.) and Mussoorie Rock phosphate (R.P.) separately at different doses. Yield of crop
in both the years increased significantly due to bacterial inoculation. Maximum grain yield was recorded in Jaya variety under
S.S.P. and R.P. when treatments were at the dose of 43.75 and 17.5 kg P ha−1 respectively while the same in IR-8 variety under S.S.P. and R.P. treatments were at the dose of 35 and 17.5 kg P ha−1 respectively. Maximum straw yield was produced by Jaya variety when 35 and 43.75 kg P ha−1 in the form of S.S.P. and R.P. respectively were applied. Highest straw yield of IR-8 variety was obtained after the application
of 17.5 kg P ha−1 (S.S.P. and R.P.) in combination with phosphate solubilizing bacteria. Bacterial inoculation decreased the phosphorus availability
in 1 st year but increased the same in 2nd year. Phosphorus content in grains was significantly enhanced in both the trials.
Maximum uptake of phosphorus by grains was noted in Jaya variety at the dose of 47.5 kg P ha−1 and in IR-8 variety at the dose of 52.5 kg P ha−1 under S.S.P. treatment, while 8.75 and 35 kg P ha−1 in the form of R.P. yielded similar results in Jaya and IR-8 varieties respectively. Phosphorus at the dose of 35 kg ha−1 was found to cause more P-uptake by straw in both S.S.P. and R.P. treatments. The various data from the experiment conclusively
proved that the bacterium in combination with R.P. produced the desired effect more prominently than when bacterium applied
in combination with S.S.P. 相似文献
944.
H. G. Petering E. Giroux H. Choudhury E. E. Menden 《Biological trace element research》1982,4(2-3):221-232
Rats were fed a purified egg white-based diet containing 5 ppm Cu and 2, 14, or 57 ppm Zn. Zinc and copper balances were determined
for eight consecutive weekly trial periods. The zinc-deficient group almost ceased to gain weight and was in slightly negative
zinc balance. Groups of rats fed 14 and 57 ppm Zn gained weight at equal rates. These groups were in strongly positive zinc
balance for four weeks; thereafter, they fed 57 ppm Zn retained about two times as much zinc as did the group fed the diet
containing 14 ppm Zn. All groups were in null or slightly negative copper balance throughout the trial. These results suggest
that zinc accumulation may be homeostatically controlled to a level in excess of that needed for maximum growth. 相似文献
945.
1. ATP synthesis (monitored by luciferin-luciferase) can be elicited by a single turnover flash of saturating intensity in chromatophores from Rhodopseudomonas capsulata, Kb1. The ATP yield from the first to the fourth turnover is strongly influenced by the phosphate potential: at high phosphate potential (?11.5 kcal/mol) no ATP is formed in the first three turnovers while at lower phosphate potential (?8.2 kcal/mol) the yield in the first flash is already one half of the maximum, which is reached after 2–3 turnovers.2. The response to ionophores indicates that the driving force for ATP synthesis in the first 20 turnovers is mainly given by a membrane potential. The amplitude of the carotenoid band shift shows that during a train of flashes an increasing ΔΨ is built up, which reaches a stationary level after a few turnovers; at high phosphate potential, therefore, more turnovers of the same photosynthetic unit are required to overcome an energetic threshold.3. After several (six to seven) flashes the ATP yield becomes constant, independently from the phosphate potential; the yield varies, however, as a function of dark time (td) between flashes, with an optimum for td = 160–320 ms.4. The decay kinetics of the high energy state generated by a long (125 ms) flash have been studied directly measuring the ATP yield produced in post-illumination by one single turnover flash, under conditions of phosphate potential (?10 kcal/mol), which will not allow ATP formation by one single turnover. The high energy state decays within 20 s after the illumination. The decay rate is strongly accelerated by 10?8 M valinomycin.5. Under all the experimental conditions described, the amplitude of the carotenoid signal correlates univocally with the ATP yield per flash, demonstrating that this signal monitores accurately an energetic state of the membrane directly involved in ATP synthesis.6. Although values of the carotenoid signal much larger than the minimal threshold are present, relax slowly, and contribute to the energy input for phosphorylation, no ATP is formed unless electron flow is induced by a single turnover flash.7. The conclusions drawn are independent from the assumption that a ΔΨ between bulk phases is evaluable from the carotenoid signal. 相似文献
946.
F.M.A.H. Schuurmans Stekhoven H.G.P. Swarts J.J.H.H.M. De Pont S.L. Bonting 《生物化学与生物物理学报:生物膜》1980,597(1):100-111
can be phosphorylated by its substrate ATP as well as by its product inorganic phosphate. The maximal capacity for phosphorylation by either of these two substances is one mol phosphate per mol enzyme. In order to investigate whether the enzyme molecule possesses only one phosphorylation site common to ATP and Pi, or two phosphorylation sites, one for ATP and one for Pi, dual phosphorylation of the enzyme has been carried out. Under conditions, which are maximally favourable for each type of phosphorylation, successive phosphorylation by Pi and ATP leads to a maximal incorporation of only one mol phosphate per mol enzyme. The phosphorylation capacity for ATP decreases by the same amount as the Pi-phosphorylation level increases, without an effect on the apparent affinity for ATP.The results can be explained by assuming either a single common phosphorylation site for Pi and ATP, or a conformational change of the enzyme following phosphorylation by Pi, which excludes phosphorylation by ATP. 相似文献
947.
The temperature dependence of sodium-dependent and sodium-independent d-glucose and phosphate uptake by renal brush border membrane vesicles has been studied under tracer exchange conditions. For sodium-dependent d-glucose and phosphate uptake, discontinuities in the Arrhenius plot were observed. The apparent activation energy for both processes increased at least 4-fold with decreasing temperature. The most striking change in the slope of the Arrhenius plot occurred between 12 and 15°C. The sodium-independent uptake of d-glucose and phosphate showed a linear Arrhenius plot over the temperature range tested (35–5°C). The behavior of the transport processes was compared to the temperature dependence of typical brush border membrane enzymes. Alkaline phosphatase as intrinsic membrane protein showed a nonlinear Arrhenius plot with a transition temperature at 12.4°C. Aminopeptidase M, an extrinsic membrane protein exhibited a linear Arrhenius plot. These data indicate that the sodium-glucose and sodium-phosphate cotransport systems are intrinsic brush border membrane proteins, and that a change in membrane organization alters the activity of a variety of intrinsic membrane proteins simultaneously. 相似文献
948.
Anil Kumar R.R. Ernst K. Wüthrich 《Biochemical and biophysical research communications》1980,95(1):1-6
The recently developed technique of two-dimensional (2D) cross-relaxation spectroscopy is utilized for systematic measurements of selective nuclear Overhauser enhancements (NOE) in the high resolution 1H nuclear magnetic resonance (NMR) spectra of biological macromolecules in solution. Compared to conventional one-dimensional NOE studies, the 2D NOE experiment has the principal advantage that it avoids detrimental effects arising from the limited selectivity of preirradiation in crowded spectral regions. Furthermore, it yields with a single instrument setting a complete network of NOE's between all the protons in the macromolecule. The resulting information on intramolecular proton-proton distances provides a new avenue for studies of the spatial structures of biopolymers. 相似文献
949.
950.
Andrew D. Beavis 《Journal of bioenergetics and biomembranes》1992,24(1):77-90
The mitochondrial inner membrane possesses an anion channel (IMAC) which mediates the electrophoretic transport of a wide variety of anions and is believed to be an important component of the volume homeostatic mechanism. IMAC is regulated by matrix Mg2+ (IC50=38 µM at pH 7.4) and by matrix H+ (pIC50=7.7). Moreover, inhibition by Mg2+ is pH-dependent. IMAC is also reversibly inhibited by many cationic amphiphilic drugs, including propranolol, and irreversibly inhibited byN,N-dicyclohexylcarbodiimide. Mercurials have two effects on its activity: (1) they increase the IC50 values for Mg2+, H+, and propranolol, and (2) they inhibit transport. The most potent inhibitor of IMAC is tributyltin, which blocks anion uniport in liver mitochondria at about 1 nmol/mg. The inhibitory dose is increased by mercurials; however, this effect appears to be unrelated to the other mercurial effects. IMAC also appears to be present in plant mitochondria; however, it is insensitive to inhibition by Mg2+, mercurials, andN,N-dicyclohexylcarbodiimide. Some inhibitors of the adenine nucleotide translocase also inhibit IMAC, including Cibacron Blue, agaric acid, and palmitoyl CoA; however, atractyloside has no effect. 相似文献